The present invention relates to a motor and a washing machine using the same.
A washing machine is an apparatus that washes laundry using washing water and friction. Recently, drum-type washing machines have become popular. In a drum-type washing machine, laundry is held in a drum which lies sideways, and when the drum is rotated, laundry is raised and dropped. The opening of the drum is located at the front of the washing machine. To support the drum, a motor shaft which connects to the drum and its connection must be reliable.
Some drum-type washing machines use outer rotor-type motors. The motor is disposed at the rear of a tub, and includes a stator which is fixed to the tub and a rotor which is connected to the drum. The rotor is fixed to a frame by means of a separate bushing, and the motor shaft is fixed to the bushing. The motor shaft is inserted in and rotatably supported by the bushing, passes through the tub, and is fixed to the drum.
If the bushing is made of a resin material, the concentricity of the motor shaft can be compromised by the bushing wearing over time, especially if a length of the motor shaft which is supported by the bushing is short. While a simple way to improve the reliability of the motor shaft may be to lengthen the amount of the motor shaft which is in contact with the bushing, this contact area cannot be lengthened indefinitely.
When the motor shaft is not firmly supported by the bushing, the clearance between the motor shaft and the bushing increases so that the angle between the motor shaft and the bushing is slightly offset. The offset causes a drop in concentricity and an increase in eccentricity of the bushing and motor shaft. Thus, when there is a predetermined clearance between the motor shaft and bushing, there is a greater eccentricity between the rotor fixed to the end of the motor shaft and the stator when the motor rotates.
An increased eccentricity means that even when the motor shaft is supported by the bushing, it can move differently from the bushing, so that the rotation of the motor can lead to an abnormal rotation of the tub and drum, which can cause vibration and noise during operation of the washing machine. This is especially true for the rotor, whose eccentricity (caused by eccentricity of the motor shaft) will cause increased vibration and noise during operation of the motor.
Also, if an clearance between the motor shaft and bushing increases, or an unevenness of the clearance increases so that the position of the rotor is not firmly supported, a signal from a Hall sensor that is installed on the stator is not properly detected, leading to faulty outputs of motor control algorithms and ultimately, to the washing machine operating incorrectly due to defective operation of the motor.